1. Field of the Invention
The present invention relates to the hydroformylation of allyl alcohol to product comprising mainly 4-hydroxybutyraldehyde (herein HBA) using a rhodium complex catalyst and a bidendate diphosphine ligand such as a (isopropylindene-2,3-dihydroxy-1,4-diphenylphosphine)butane (herein DIOP) ligand having a bite angle of 100-120 degrees, under reaction conditions wherein a relatively high liquid phase concentration of carbon monoxide is maintained during the reaction.
2. Description of the Prior Art
It is known to react allyl alcohol with a carbon monoxide and hydrogen mixture to form hydroxybutyraldehyde; various catalyst formulations have been employed, most notably a rhodium complex together with a phosphine ligand. Commonly employed phosphine ligands are trisubstituted phosphines such as triphenyl phosphine. Patents which are illustrative of such technologies include U.S. Pat. Nos. 4,567,305, 4,215,077, 4,238,419 and the like.
The hydroformylation of allyl alcohol to hydroxybutyraldehyde using rhodium complex catalysts and DIOP ligand is shown in the art, notably in Japan Kokai 06-279345 and 06-279344.
Butanediol is produced commercially by a process which involves hydroformylation of allyl alcohol to 4-hydroxybutyraldehyde and hydrogenation of the 4-hydroxybutraldehyde to 1,4- butanediol (herein BDO). Usually some methyl propanediol (herein MPD), itself a useful material, is formed from methyl hydroxypropionaldehyde (HMPA) also formed in the hydroformylation. A severe disadvantage of prior processes has been the formation of C.sub.3 products such as normal propanol, propionaldehyde, and the like during the hydroformylation. Formation of these materials effectively represents a yield loss in the process which can have a severe adverse effect on the process economics.